There's a long-held myth that Johannesburg is the globe's largest urban forest, resplendent with an annual purple Jacaranda show. But before the planting of these (alien) trees for timber during the Gold Rush in the 19th Century, Johannesburg was a rich and varied grassland—a biome [community of plants and animals] that is one of the least protected in South Africa. Fortunately, the Department of Environmental Affairs prohibits plantation forestry in our grasslands, because of the negative impact it has on water resources and biodiversity.